Clavamox. Vets and pet parents like clavamox for a few reasons. It's cheap. It can be given as pills OR liquid. It's not "bad" tasting, as compared to medicines such as baytril or clindamycin (antirobe), so the cat doesn't foam up and gag.
The down side is the common side effects of diarrhea and stomach upset. Most cats can tolerate it okay. Most vets will not tell you to give the medicine with food, but that is important, it will help with the stomach upset. The diarrhea can be counteracted by giving a probiotic during and for a week or so after the course of the antibiotic.
In my experience, the more a cat has to take clavamox, the higher the chance of an adverse reaction. My herpes boy used to have pretty bad secondary infections when he had a herpes flare up. I would put him on clavamox and that worked well. But the fourth time he had to have the clavamox he got very sick on it, so I won't ever give it to him again.
My FLUTD kitty has had a few UTIs. Clavamox clears them up. She even likes the pills, I put them in a little wet food, she eats the wet food, saves the pill for last and scoops it up. She's also taken clavamox a couple of times for an ear infection. (chronic problem, due to a yeast infection that went untreated for who knows how long, before I adopted her) She's never had any problem with it..until the last time she had it, she got very lethargic, and nauseous while on it. So I won't give it to her again.
My other adult...I know she can't have clavamox because one time, when the above mentioned cat was on it, I gave the other cat the food with the clavamox in it by mistake. This cat didn't mind the pill either she gobbled it up, but then vomited half an hour later. So the one time she's needed antibiotics since living with me, she had Baytril.
So..in my opinion, use clavamox if the vet prescribes it, but give it with food and use a probiotic. If the cat gets very sick and symptoms don't improve, call the vet and ask for a different antibiotic and don't use clavamox again. If kitty tolerates it okay, then it's all good.